A twistlock and corner casting together form a standardized rotary connector for securing and locking shipping containers onto one another when stacked e.g. on a container ship, semi-trailer truck or railway container train. The corner casting constitutes a female part of the connector and is fitted to the container itself, one in each of the eight corners. It has no moving parts, only oval holes in its side-, top- and bottom surfaces respectively. The male component is a twistlock, which is arranged to engage the corner casting and comprises a rotary top portion and a rotary bottom portion, and is inserted through the hole. Then, the top portion or the bottom portion is rotated 90° to lock the twistlock to the corner casting. Referring to FIG. 1, according to established methods, the twistlocks are manually introduced into the four lowermost corner castings of a container on the quay and subsequently locked into place. In this position, the twistlock has one portion being locked inside the corner casting, and one portion protruding in a downward direction out of said corner casting. The container is then moved to the ship, normally by means of an STS crane (ship to shore crane) with a spreader, and is to be superimposed onto an already loaded container on the ship. The protruding portions of each of the four twistlocks of the container to be loaded are then inserted into the uppermost corner castings of the container already positioned on the ship, thereby securing the two containers onto each other and preventing them from e.g. shifting away from each other or slipping into the sea.
Since the 1950's, the male locking device of the rotary connector is further developed to avoid having to rotate the bottom portion manually when attaching the lock to a corner casting. The dimensions of the corner castings are standardized in ISO 1161:1984.
Document DE10 2009 019 955 A1 discloses a locking device having a housing and a vertical locking member rotary mounted in the housing. By rotating the locking member, the locking device can engage the corner casting or be disengaged there from. A stop member, which can be brought into engagement with the locking member, is movable by means of a guide member, so that the stop member at one position prevents the locking member from rotating and at another position permits the rotation.
Document EP 2 910 421 A2 discloses a locking device comprising a housing and a locking mechanism, which by means of a manually operated control lever can be shifted between a locking position, where the locking mechanism locks the locking device to a corner casting, and an open position, where the locking mechanism and the corner casting are free from each other. The locking mechanism includes at least one pivotal arm with a hook end. When two arms are used, they are swung in opposed directions. The locking device is suitable for mounting on a vehicle or similar fastening location for a shipping container that is lowered down on it. However, there is no disclosure as to how the locking device is secured to the vehicle or similar fastening location.
Document EP 2 143 665 A1 discloses a locking device for securing together upper and lower shipping containers to prevent a stack of shipping containers from shifting away from one another or slipping into the sea from a container ship. The locking device includes interconnected upper and lower retaining members, each adapted to be inserted into a hole in a corner piece of a respective one of the upper and lower shipping containers, and at least one swing member disposed inside the lower retaining member. The upper retaining member has a top end aligned with a bottom end of the lower retaining member along an axial line of the locking device. The swing member includes a lower pivot portion connected pivotally to the lower retaining member, and an upper engaging portion which is proximate to the axial line in a non-engaging position and when the axial line of the locking device is substantially vertical, and which moves away from the axial line in an engaging position when the axial line of the locking device is inclined and non-vertical.
Document WO 2005/054086 A1 discloses a method for the automatic locking and unlocking of coupling pieces, whereby an at least partial locking of the coupling pieces occurs on a displacement of the shipping container in the plane of the deck, which can be reversed by an opposing displacement of the container. A fully-automatic coupling piece comprises a coupling projection, for vertical connection of the container, with anchoring lugs, running in the transverse direction of the container of which at least one anchoring lug may be displaced. The aim is to use a relative displacement of the container, in the direction of the deck, for carrying out an automatic locking of the container. On reversal of said displacement, an equally automatic unlocking of the container is possible.
Document WO 2011 110743 A1 discloses a coupling device for coupling shipping containers, particularly for coupling containers used in container ships and land transport. The coupling device includes a fastening piece formed in the upper part of its body part, by which the body part can be fastened in a corner casting in a corner of the container by rotating the body part around its vertical axis, whereby the fastening piece is locked in the corner piece of the container. The body part includes a planar coupling plate formed between its upper part and lower part, and the body part further includes a cam part below the coupling plate. In addition, body part is fitted with a first rotatable lever-like locking part for preventing and/or releasing the motion of the body part, and the body part includes a second rotatable lever-like locking part for enabling and/or preventing the motion of the body part. The second lever-like locking part is either directly or indirectly in contact with the first lever-like locking part so that, as the first lever-like rotates, the second lever-like locking part is also able to rotate for enabling the locking mode and the unlocking mode. In the second lever-like locking part, there is formed a protrusion for receiving vertical forces between the containers.
U.S. Pat. No. 8,228,185 B2 and U.S. Pat. No. 8,228,186 B2 disclose systems for remote control of the locking and unlocking of a lock for a shipping container.